The combat uses for helicopter aircraft have changed dramatically over the years to include contact with opposing forces, including reconnaissance and combat aircraft assistance of troops on the front line. This type of use subjects helicopters to numerous threats, and therefore new helicopter designs incorporate offensive weapons, such as Gatling guns and rocket launchers.
Initially, the primary control of helicopter weapons was accomplished by the pilot aiming the aircraft at the target prior to firing. Correction for misses was accomplished by the pilot adjusting the attitude of the aircraft prior to expending additional ordnance. As technology developed, tracking and sensing systems were used to locate the target and determine the aircraft attitude necessary to aim the weapon so as to account for outside forces acting on the ordnance, e.g., wind, aircraft speed, etc. Such a system typically displays a "cross-hair" indicative of actual aircraft attitude and a geometric shape indicative of the required aircraft attitude to provide a high probability of striking the target with the weapon. The pilot is required to maneuver the aircraft so as to place the cross-hair in the firing solution defined by the shape prior to firing the weapon. The aiming instructions e.g., cross-hair and geometric shape, are typically displayed on a control panel, a heads-up display, or helmet-mounted display which provides the pilot with visual information relating to the target position, own ship attitude, heading, speed and altitude.
Although such aiming systems improved weapons delivery accuracy, the pilot is still under a significant burden to regulate aircraft heading and pitch attitude. It is well-known that a skilled helicopter pilot can control aircraft attitude within about 1 degree of pitch and yaw. Although this may seem very accurate control, a 1 degree variation in pitch or yaw will have a significant effect on the trajectory of a projectile.
One solution to the above mentioned problem of weapons delivery accuracy is to provide the aircraft weapons systems with articulated mountings, e.g. rocket launchers and gatling guns articulated in azimuth and/or elevation. The fire control solution is then used to control the pointing direction of the weapon mount to improve weapons delivery accuracy and reduce pilot workload. However, when the weapons mount reaches the limits of its travel, i.e., constraint limit, the fire control system is no longer capable of controlling the weapon mount to point the weapon directly at the firing solution.
Additionally, certain sensors used for target tracking and weapons targeting have constraint limits. For example, a nose mounted, forward looking radar may only be able to detect and track targets within a limited area relative to the nose of the aircraft, e.g., plus or minus 130 degrees. If a target is allowed to move outside the field of operation defined by the sensor constraint limits, the sensor will lose track of the target.